world power vs great power

world power and great power both are nouns.

Word	Noun	Adjective	Verb	Adverb
world power	Yes	No	No	No
great power	Yes	No	No	No

As nouns, world power and great power are synonyms defined as:

world power and great power: a state powerful enough to influence events throughout the world

Other synonyms of world power include major power, power, superpower.

world power (noun)	great power (noun)
a state powerful enough to influence events throughout the world	a state powerful enough to influence events throughout the world